This invention relates in general to a manifold assembly for a fuel cell power plant, and deals more particularly with an inter-stack manifold assembly in a PEM fuel cell power plant which minimizes both weight and volume while ensuring uniform distribution of reactants to adjacent cell stack assemblies.
Electrochemical fuel cell assemblies are known for their ability to produce electricity and a subsequent reaction product through the interaction of a reactant fuel being provided to an anode electrode and a reactant oxidant being provided to a cathode electrode, generating an external current flow there-between. Such fuel cell assemblies are very useful due to their high efficiency, as compared to internal combustion fuel systems and the like, and may be applied in many fields. Fuel cell assemblies are additionally advantageous due to the environmentally friendly chemical reaction by-products, typically water, which are produced during their operation. Owing to these characteristics, amongst others, fuel cell assemblies are particularly applicable in those fields requiring highly reliable, stand-alone power generation, such as is required in space vehicles and mobile units including generators and motorized vehicles.
Typically, electrochemical fuel cell assemblies employ reactants such as a hydrogen-rich gas stream as a fuel and an oxygen-rich gas stream as an oxidant, whereby the resultant reaction by-product is water. Such fuel cell assemblies may employ a membrane consisting of a solid polymer electrolyte, or ion exchange membrane, disposed between the anode and cathode electrodes formed of porous, electrically conductive sheet materialxe2x80x94typically, carbon fiber paper. One particular type of ion exchange membrane is known as a proton exchange membrane (hereinafter PEM), such as sold by DuPont under the trade name NAFION(trademark) and well known in the art. Catalyst layers are formed between the PEM and each electrode to promote the desired electrochemical reaction. The catalyst layer in a fuel cell assembly is typically a carbon supported platinum or platinum alloy, although other noble metals or noble metal alloys may be utilized. In order to control the temperature within the fuel cell assembly, a water coolant is typically provided to circulate about the fuel cell assembly.
In the typical operation of a PEM fuel cell assembly, a hydrogen rich fuel permeates the porous electrode material of the anode and reacts at the catalyst layer to form hydrogen ions and electrons. The hydrogen ions migrate through the PEM to the cathode electrode while the electrons flow through an external circuit connected to a load. At the cathode electrode, the oxygen-containing gas supply also permeates through the porous substrate material and reacts with the hydrogen ions and the electrons from the anode electrode at the catalyst layer to form the by-product water. Not only does the PEM facilitate the migration of these hydrogen ions from the anode to the cathode, but the ion exchange membrane also acts to isolate the hydrogen rich fuel from the oxygen-containing gas oxidant. The reactions taking place at the anode and cathode catalyst layers may be represented by the following equations:
Anode reaction: H2xe2x86x922H++2e
Cathode reaction: xc2xdO2+2H++2exe2x86x92H2O
In practical applications, a plurality of planar fuel cell assemblies are typically arranged in a stack, commonly referred to as a cell stack assembly. The cell stack assembly may be surrounded by an electrically insulating housing that defines the various manifolds necessary for directing the flow of a hydrogen-rich fuel and an oxygen-rich oxidant to the individual fuel cell assemblies, as well as a coolant stream. A fuel cell power plant may typically be comprised of the fuel cell stack assembly, reactant storage vessels, reactant control valves, reactant propulsion devices, coolant pumps, heat exchangers, coolant degassifiers or demineralizers, sensors for measuring reactant concentrations, temperatures, pressures, current, voltage, and a microprocessor that controls the operation of the fuel cell power plant.
As will be appreciated by one so skilled in the art, tying these differing components into a cohesive fuel cell power plant operating within specific design parameters results in a complex and oftentimes cumbersome structure.
Specifically, the many components of a fuel cell power plant typically result in a weighty structure having a considerable volume, thereby making integration of the fuel cell power plant in motor vehicles and the like difficult. In addition, many fuel cell power plants include two or more cell stack assemblies in electrical communication with one another, each of these cell stack assemblies requiring a carefully controlled supply and exhaust of reactant fuel and oxidant to operate efficiently.
With the forgoing problems and concerns in mind, the present invention therefore seeks to decrease the weight and volume associated with a multiple cell stack assembly fuel cell power plant, while ensuring the uniform distribution of fuel and oxidant reactants.
It is an object of the present invention to increase the operational efficiency of a fuel cell power plant.
It is another object of the present invention to reduce the height of a fuel cell power plant.
It is another object of the present invention to reduce the weight and volume of a fuel cell power plant.
It is another object of the present invention to ensure the uniform distribution of reactants to cell stack assemblies comprising a fuel cell power plant.
It is another object of the present invention to provide a center structural support for a fuel cell power plant.
It is another object of the present invention to provide a center structural support for a fuel cell power plant which is capable of carrying current from one cell stack assembly to another in a fuel cell power plant.
It is another aspect of the present invention to increase the vibrational stability of a fuel cell power plant.
According to one embodiment of the present invention, a fuel cell power plant includes a first cell stack assembly having a plurality of planar fuel cells in electrical communication with one another and a second cell stack assembly having a plurality of planar fuel cells in electrical communication with one another. An inter-stack manifold assembly is disposed between the first and second cell stack assemblies and provides an electrical pathway between the first and second cell stack assemblies. A baffle is formed internally to the manifold assembly for diverting a substantially uniform proportion of a reactant stream to the first and second cell stack assemblies while diverting an exhausted reactant stream from the first and second cell stack assemblies.
These and other objectives of the present invention, and their preferred embodiments, shall become clear by consideration of the specification, claims and drawings taken as a whole.